Analog Devices Inc. AD7870BQ

Overview

AD7870BQ from Analog Devices is a complete monolithic 12-bit sampling analog-to-digital converter (ADC) with integrated track-and-hold amplifier, laser-trimmed internal clock, and on-chip 3 V buried Zener reference. It delivers 100 kHz sampling rate, 72 dB SNR at 10 kHz input, ±3 V bipolar input range, and 57 ns data access time-enabling high-fidelity signal acquisition in DSP-based data acquisition systems.

For engineers reviewing the AD7870BQ datasheet, AD7870BQ pinout, AD7870BQ application, or AD7870BQ equivalent, this page provides verified technical context, validated pin functions, confirmed dynamic and dc specifications, real-world interface timing constraints, and two rigorously cross-referenced alternative parts for system-level design continuity.

Technical Context

The AD7870BQ implements a successive approximation register (SAR) architecture with a voltage-output DAC and high-speed comparator. Its internal 3 V buried Zener reference is temperature-compensated (±35 ppm/°C max for B-grade), laser-trimmed to ±10 mV, and supplies both DAC bias and bipolar offset correction.

Conversion is initiated asynchronously via CONVST rising edge or CS falling edge, with total throughput time ≤10 μs (8 μs conversion + 2 μs track-and-hold acquisition). The device supports three digital output formats-12-bit parallel, two 8-bit bytes, or serial-each governed by the 12/8/CLK and HBEN control pins and validated across −40°C to +85°C.

Key Specifications

Pinout & Package

AD7870BQ is housed in a 24-pin, 0.3-inch-wide hermetic dual-in-line package (DIP) rated for industrial temperature operation (−40°C to +85°C). Pin assignments are identical across DIP and SOIC variants per Figure 2 of Rev. C datasheet.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit sampling ADC applications.

Compared with AD7870BQ, AD7870KN trades hermetic reliability for lower cost in benign environments, while AD7875BQ replaces bipolar capability with unipolar input support and binary coding-neither is pin-compatible, and PCB layout changes are required for either substitution.

Availability

AD7870BQ is available at Aetrix Electronics and suitable for industrial data acquisition, test & measurement equipment, medical instrumentation, and DSP-based signal analysis requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD7870BQ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing ICs for precision measurement and control applications.

The AD7870BQ belongs to the LC2MOS Complete Sampling ADC family, designed specifically for high-accuracy, low-power data acquisition in industrial, instrumentation, and medical systems where integration, dynamic performance, and temperature stability are critical.

FAQ

What is the maximum analog input frequency supported by the AD7870BQ without aliasing?

The AD7870BQ supports full-power analog input signals up to 50 kHz, consistent with its 100 kHz sampling rate and Nyquist criterion. Its track-and-hold amplifier has a 0.1 dB cutoff frequency of 500 kHz, ensuring minimal amplitude and phase error across the entire input bandwidth. This allows the AD7870BQ to accurately digitize fast transients and wideband sensor outputs while maintaining 12-bit resolution.

Does the AD7870BQ require external clock components for basic operation?

No, the AD7870BQ does not require external clock components for basic operation. It features an on-chip laser-trimmed oscillator that guarantees conversion times between 6.5 μs (min) and 9 μs (max) without any external timing elements. An external TTL-compatible clock may be applied to the CLK pin only if precise synchronization with a system master clock is needed-otherwise, tying CLK to VSS activates the internal oscillator.

How is the reference voltage used internally in the AD7870BQ?

The AD7870BQ's internal 3 V buried Zener reference serves two critical functions: it provides the reference voltage for the 12-bit DAC within the SAR core, and it supplies the dc bias required for bipolar operation of the analog input stage. The REF OUT pin makes this 3.00 V ±10 mV reference available externally, supporting up to 500 μA load current-enabling use as a stable reference for companion circuitry such as input amplifiers or DACs.

Can the AD7870BQ interface directly with an 8-bit microprocessor bus?

Yes, the AD7870BQ supports direct 8-bit microprocessor interfacing via its byte-mode output. When the 12/8/CLK pin is set to 0 V or −5 V and HBEN is controlled appropriately, the device outputs two sequential 8-bit bytes (high byte first, then low byte) on DB7–DB0. This eliminates the need for external latches or data-width translators when connecting to Intel 8085, Zilog Z80, or compatible 8-bit CPUs.

What is the meaning of "BQ" in the AD7870BQ part number?

The "BQ" suffix in AD7870BQ denotes a hermetic ceramic dual-in-line package (DIP) qualified for industrial temperature operation (−40°C to +85°C). The "B" grade indicates the device meets tighter dc accuracy specifications-including ±1/4 LSB typical integral nonlinearity and ±35 ppm/°C reference temperature coefficient-while "Q" specifies the hermetic, side-brazed ceramic package construction for enhanced moisture resistance and long-term reliability in harsh environments.